Early Cretaceous (Aptian to Albian) vegetation and climate change in Central Africa: Novel palynological evidence from the Doseo Basin

Abstract

With the break‐up of the continents of Africa and South America and the gradual opening of the Atlantic Ocean in the late Aptian to early Albian, the global palaeoclimate and palaeogeographical patterns changed greatly. Whether and when a humid belt prevailed in the palaeoequator region during this period has been argued for a long time. The Doseo Basin, located in the Central African Rift system, is important for understanding the palaeoclimate of Central Africa during the Early Cretaceous. Here, a systematic palynological analysis of boreholes K‐1 and KE‐101 in the Doseo Basin was conducted to reconstruct the vegetation and climate change during the middle Aptian to early Albian in Central Africa. Relatively abundant fossil palynomorphs were obtained, and 76 species belonging to 67 genera were identified. Gymnosperms were found to be dominant in the palynoassemblage of boreholes K‐1 and KE‐101, and Classopollis was the most abundant in this group. Among fern spores, the ribbed spores accounted for a high proportion. Additionally, a small amount of angiosperm pollen grains was also found. Based on the characteristics of the palynomorphs, two assemblages were identified, probably spanning from middle Aptian–early Albian. The characteristics of the spore and pollen fossils, especially the decrease of Classopollis in boreholes K‐1 and KE‐101, suggest an obvious change in climate, from relatively arid to humid during the late Aptian to early Albian (within the interval 2215–2220 m of borehole K‐1). The climate change reflected by the palynological spectra in the Doseo Basin from dry to wet is consistent with that of the results from South America. This study further proves that the climate near the equator in the southern hemisphere began to change from the earlier relative drought to humid conditions with the gradual opening of the Atlantic Ocean during late Aptian to early Albian, and a humid climate zone was distributed from east to west in the equatorial region of the southern hemisphere.